Well I just found out today that my starboard manifold is causing some hydrolocking on my motor so my winter project is to replace the exhAust . Currently I have stock 454's with stock manifolds and risers on them and bravo drives. The risers connect to a corsa (tailpipe?) system. I have never ordered exhaust for boats. I don't really think I can afford to upgrade but am going to have a look around. What different things do you need to know to order exhaust for a twin engine setup? Would 454 mag exhaust be the same as regular 454?

call scott at speed custom marine 850 875 0381 he may have dinged after market exhaust from stainless marine which is a nice one to go with for get stock, also try bill at Diamond marine 302 521 0123 scotts in fl and bill is in LI NY there both great guys to work with.

I can help, give me a call. 302-521-0123
Thanks Artie

Is the manifold bad or is the gasket leaking at the manifold/riser connection? Regular 454 and 454 MAG exhaust is the same. For a low cost upgrade, look for 496 take-offs. Earlier 496 manifolds were aluminum. All the risers are stainless.

496 stock take off exhaust will fit 454's also?

Yes, and it is a great low-cost alternative to more expensive aftermarket systems. If you're running mild 454s the Hp difference between the 496 system and something like an EMI or Stainless Marine system will be negligible. The older aluminum systems are the more desirable and generally sell for between $450-650 a set, with risers. The cast iron systems are the exact same castings, the just weigh more, and generally sell for around $200 less per set.

And these will be a nice Hp upgrade over your stock 454 cast iron manifolds and risers.

So a set of stock 496 risers and manifolds will open up stock 454's more than the current setup? Didnt know 454's were that constricted.....thats awesome though.

The stock 496 exhaust is much better, and lighter, than the older cast iron stock stuff.

All the 454 and 502 black Merc engines used the same exhaust and the 496 exhaust will work with any 454/502. You may have to change some hose routing a little bit.

That being said, if its the original exhaust and its never been off, it will most likely be a beotch to get the bolts out. Start soaking them with PB Blaster everyday for a week before you start trying to get the bolts out.

My 1985 manifolds came right off.... Everywhere but the damn rubber exhaust hose used for the tails. That was a SOB! Any advice on how to separate that joint without cutting/melting the rubber?

If the 496 exhaust is interchangeable with the standard 454/502 exhaust why is it that every aftermarket exhaust company makes a specific 496 exhaust system?

Something has to be different.